2. Code Structure Overview
===========================

This chapter will help you understand the code organization of the project, making it easier for you to perform secondary development and feature expansion.

.. note::
   This project is based on the **CMake** build system, using **FreeRTOS** real-time operating system and **LVGL** graphics library.

Project Structure
------------------

The project adopts a modular design, mainly divided into the following parts::

   LAFVIN-PICO-Development-Kit/
   ├── main.c                          # Main program entry
   ├── CMakeLists.txt                  # CMake build configuration
   ├── components/                     # Function components directory
   ├── generated/                      # LVGL auto-generated UI code
   ├── Hardware Driver Layer
   │   ├── st7796.c/h                 # Display driver (ST7796U)
   │   ├── gt911.c/h                  # Touch screen driver (GT911)
   │   └── ws2812.pio                 # RGB LED driver (WS2812)
   ├── LVGL Porting Layer
   │   ├── lv_conf.h                  # LVGL configuration file
   │   ├── lv_port_disp.c/h           # Display interface porting
   │   └── lv_port_indev.c/h          # Input device porting
   ├── FreeRTOS Configuration
   │   ├── FreeRTOSConfig.h           # FreeRTOS configuration
   │   └── FreeRTOS_Kernel_import.cmake
   └── SDK Import
       └── pico_sdk_import.cmake       # Pico SDK import script

Core Files Description
---------------------------

**main.c** - Program entry, includes system initialization, task scheduling, dual-core cooperation and application logic

**CMakeLists.txt** - CMake build configuration, defines compilation options and dependency libraries

Main Code Modules
------------------

**Hardware Driver Layer**

* **st7796.c/h** - 3.5-inch TFT display driver (via SPI communication)
* **gt911.c/h** - Capacitive touch screen driver (via I2C communication)
* **ws2812.pio** - RGB LED driver (using PIO for precise timing)

**LVGL Porting Layer**

* **lv_conf.h** - LVGL configuration file (memory, color depth, feature switches)
* **lv_port_disp.c/h** - Display interface porting (connects to display driver)
* **lv_port_indev.c/h** - Input interface porting (connects to touch screen driver)

**Function Components**

* **components/** - Contains hardware demo and calculator application code
* **generated/** - LVGL UI design tool auto-generated interface code

**System Configuration**

* **FreeRTOSConfig.h** - FreeRTOS configuration (tasks, memory, dual-core support)
* **pico_sdk_import.cmake** - Pico SDK import script

Hardware Resources Overview
------------------------------------

**Pin Assignment**

* **GP2-GP7, GP10-GP11**: SPI0 connected to TFT screen
* **GP8-GP9**: I2C0 connected to touch screen
* **GP12**: RGB LED (WS2812)
* **GP13**: Buzzer
* **GP14-GP15**: Buttons (BTN2, BTN1)
* **GP16-GP17**: LED indicators (D1, D2)
* **GP26-GP27**: Joystick (X-axis, Y-axis)

For more detailed hardware resource description, please refer to :doc:`/component_list`

Code Execution Flow
---------------------------

**Startup Process**

1. Hardware initialization (clock, GPIO, peripherals)
2. Driver initialization (display, touch screen, LED)
3. LVGL initialization (register display and input devices)
4. FreeRTOS startup (create tasks and enter multitasking mode)

**Runtime Architecture**

* **Core0**: Runs LVGL tasks, handles UI updates and touch events
* **Core1**: Runs hardware monitoring tasks, handles buttons, joystick, buzzer, etc.

Dependencies
------------------

The project depends on three main libraries (configured during development environment setup):

* **Pico SDK** - RP2040 official development package
* **FreeRTOS** - Real-time operating system
* **LVGL** - Graphics library

Next Steps
------------------

* Continue learning how to compile the project → :doc:`3.编译项目`